ISSN:0309-1929    

DOI:10.1080/03091928008241177

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

I examine the geostrophic turbulence field in equilibrium with a horizontally uniform mean zonal flow driven by solar heating. The equilibrium mean vertical shear is highly supercritical, and the turbulence field has its maximum in kinetic energy at wavenumbers smaller than the wavenumbers of fastest growth predicted by linear stability theory. Wavenumber spectra obtained by averaging lengthy numerical integrations of the two-level quasi-geostrophic equations agree well with the predictions of a simple Markovian turbulence model. Analysis of the turbulence model suggests that the most energetic wavenumbers equilibrate from scattering of the temperature perturbations into higher wavenumbers by the barotropic adverting field. In the higher unstable wavenumbers, including the most supercritical, linear instability is offset chiefly by local rotations of the unstable structures by larger, more energetic eddies.

ISSN:0309-1929    

DOI:10.1080/03091928008241178

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Quasi-two-dimensional turbulence is generated in a rotating cylinder by an homogeneous distribution of bottom sources and sinks which oscillate in time. Typical Reynolds numbers reach 2000 and inertial time-scales are about an order of magnitude smaller than the Ekman spin-up time. This allows the genuine inertial effects of the flow field such as the gross spectral evolution of the energy containing eddies to be emphasized. The case of no topography is first discussed. When the fluid is steadily forced, it is observed that the energy containing scale is significantly larger than the forcing scale. Theoretical arguments for that behavior are presented. In the decaying stage the red cascade is observed and rates of interaction are measured.

ISSN:0309-1929    

DOI:10.1080/03091928008241179

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The properties of turbulent flows are strongly modified by the presence of dispersive waves the period of which can be less than the eddy-turnover time of turbulence for sufficiently large scales. Using a systematic method due to Andre, we show that the presence of such waves induces complex damping rates in stochastic models like for instance the Eddy-Damped Quasi-Normal Markovian model: in other terms, turbulence acts to renormalise both viscosity and frequency. This method is applied to spherical Rossby waves; it is found that the relative correction to Rossby frequencies, negligible at planetary scales, might become important around 1000km and tends to a limit close to 0.3 for sufficiently small scales.

ISSN:0309-1929    

DOI:10.1080/03091928008241180

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Starting from hydrostatic non-adiabatic equations for atmospheric flows, we use a matched asymptotic expansion technique, with the Kibel, Ekman and Mach numbers as small parameters, the last two of them being related in a definite way to the first one. We derive, as a first approximation, the quasi-geostrophic equation and in a second approximation the ageostrophic equation which is consistent with the scheme of expansion. A brief account is given of the various initial and boundary layers.

ISSN:0309-1929    

DOI:10.1080/03091928008241181

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The results are presented of laboratory experiments to investigate weak baroclinic waves which may occur in thermally driven flows in a rotating annulus beyond the Eady cutoff for baroclinic instability. In the system used for the experiments the Taylor number was large while the curvature ensured the presence of large gradients of potential vorticity. Stable axisymmetric flows, weak waves and strong baroclinic waves were observed depending on the values of the imposed parameters of the system. The horizontal and vertical profiles of mean zonal velocity were obtained both by measurement and from numerical simulations of the flows. The linear stabilities of flows approximating the observed flows were examined. Agreement between the laboratory observations and the linear analyses regarding the location in parameter space of the transition between different flow regimes and the structure of the flows was good, giving support to the hypothesis that the weak instabilities were due to potential vorticity gradients in the fluid.

ISSN:0309-1929    

DOI:10.1080/03091928008241182

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The turbulent thermal convection of a horizontal plane layer of electrically conducting Boussinesq fluid is considered. It is permeated by a horizontal magnetic field, which is maintained by dynamo action unaided by any externally applied electric currents. Upper bounds for the ohmic dissipation in the mean magnetic fieldMare obtained by maximisingMitself subject to a number of constraints which include power integrals derived from the governing equations. The structure of the optimal vector field depends on the magnitude of both the Rayleigh number R and a magnetic Prandtl numberqwhich is assumed to be small. Nevertheless irrespective of the value ofq, it is found thatMis bounded above according to the universal lawMℳKR3/2, whereKis a constant whose numerical value is independent of the parameters characterising the problem.

ISSN:0309-1929    

DOI:10.1080/03091928008241183

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

WAVE INSTABILITIES IN SPACE PLASMAS. Edited by P. J. Palmadesso and K. Papadopoulos, D. Reidel Publishing Company, vii + 309pp (ISBN 90-277-1028-7) 1979.

ISSN:0309-1929    

DOI:10.1080/03091928008241184

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091928008241185

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor